This movie of 26 frames shows individual defects moving around in the two-dimensional crystal formed by the membrane protein Bacteriohodopsin (purple membrane). If you watch the "clouds" moving around on the surface of the crystal carefully, you can see structure that correlates with the underlying lattice. This leads us to believe that the "clouds" are loosely bound BR molecules moving around on top of the lattice and occasionally in and out of defect sites in the lattice. The fact that loosely bound molecules can be individually resolved is a testament to the very light imaging forces possible when using small cantilevers (low thermal noise and higher quality factors) and very small amplitudes in tapping mode in liquid. Imaged using a 20 µm long cantilever with a resonance frequency in liquid of 153 kHz and an amplitude of 9 Å. Buffer conditions: 300 mM KCl, 10 mM TRIS, pH 7.8. Image size 100 x 100 nm. 10 Hz Scan Rate (51 s per frame).